1. Field of the Invention
The present invention relates to an imaging apparatus and a camera system that are capable of combining a plurality of images obtained by performing a plurality of shooting operations.
2. Description of the Related Art
Conventionally, in a shooting scene when a person is being shot in a night scene for a background, for example, to acquire an image in which brightness of both the person and the background is good, a technique for combining images acquired by shooting with flash light emitted by a flash device and images acquired without flashlight emission is discussed in Japanese Patent Application Laid-Open No. 2007-180904.
In such a technique, an image of the person with good brightness can be acquired by shooting with flash light emitted by the flash device with an amount of flashlight corresponding to the brightness of the person, and an image with good brightness of the background can be acquired by shooting with an exposure time corresponding to the brightness of the background. By performing an image combining operation by using the former image for the person portion and using the latter image for the background portion, an image having good brightness of both the person and the background can be acquired.
Further, when an image is shot with an exposure time corresponding to the brightness of the background, the exposure time becomes long and an influence of an operator's camera-shake becomes significant. Therefore, the brightness of the background is made good by dividing the exposure time, corresponding to the brightness of the background, into a plurality of parts, and then performing a plurality of shooting operations with the divided exposure time to perform the image combining operation.
However, like the technique discussed in Japanese Patent Application Laid-Open No. 2007-180904, in a case where shooting with flash light emitted by the flash device and shooting without flash light emitted by the flash device are continuously performed, and a plurality of images obtained by continuously performing a plurality of shooting operations without flash light emitted by the flash device are combined, the following problems arise. Hereinbelow, as illustrated in FIG. 4, problems will be described arising in a case where the shooting with flash light emitted by the flash device is performed at the first frame of a series of shooting operations, which includes the shooting with flash light emitted by the flash device and the shooting without flash light emitted by the flash device.
Generally, after shooting with flash light emitted by the flash device, it is desirable to perform charging of a capacitor of the flash device immediately after shooting to shorten a charging waiting time spent until the next shooting with flash light emitted by the flash device becomes possible. In a case where shooting with flash light emitted by the flash device is performed at the first frame of a series of continuous shooting operations, it is assumed that charging will be performed during the subsequent shooting without flash light emitted by the flash device, to shorten a time spent until the next shooting with flash light emitted by the flash device becomes possible. However, subsequent images obtained by shooting without flash light emitted by the flash device may be deteriorated by an influence of electric noise generated by charging (hereinafter, referred to as “charging noise”).
Thus, as illustrated in FIG. 4, instead of charging during each shooting of a series of continuous shooting operations (including a time period during which electric signals are readout from the image sensor), by charging between successive shooting operations, the shot image can be free of influence of charging noise. However, when an attempt is made to secure a sufficient charging time between the successive shooting operations, a difference in composition between the images becomes large, and, therefore, it becomes difficult to combine the images.